AIR VESSELS FOR PUMPS 



625 



being of more value than an increase in length. Also, for efficient 

 working, the water-level in the air vessel should be adjusted by adjusting 

 the air pressure, until as low as is consistent with water remaining in the 

 vessel during the first part of the suction stroke. For the air vessel to be 

 as effective as possible in preventing shock it should be so situated as to 

 provide an effective air cushion to the entrant water. Fig. 298 a, fc, and c, 



FIG. 298. Suction Air Vessels for Reciprocating Pumps. 



shows various methods of applying the air vessel. Of these (a) is very 

 little good in preventing shock, (b) is good except that the provision of a 

 right-angled bend at the entry to the suction chamber is inadvisable- 

 The best method is that illustrated at (c), since here the air vessel is in a 

 direct line with the suction pipe, while discharge either from the air 

 vessel or supply pipe takes place directly into the suction chamber 

 without the intervention of bends or elbows of any description. It may 

 be premised that the air vessel should always be placed so that a sudden 

 H.A. s s 



